A 61-YEAR-OLD grandmother allegedly took out a sledgehammer to kill her five-month-old granddaughter and when she noticed the baby was still alive slit her throat with a kitchen knife.

The Chicago Tribune reports that Alfreda Giedrocz showed no emotion as she sat in a courtroom on Monday with a Polish translator.

The paper says little Vivian Summers had been dropped off by her father, Ms Giedrocz's son-in-law, while he worked across the street in Oak Lawn, Chicago, helping Ms Giedrocz's son work on his house.

Ms Giedrocz's husband, Bill, went across the street to check on their progress when Ms Giedrock allegedly went to a closet and took out a sledgehammer that she had placed their the night before.

"The defendant then hit the victim repeatedly in the head and body with the sledgehammer," Assistant State's Attorney Michael Deno said. "Since the victim was still crying and moving, the defendant then went to the kitchen and retrieved a large carving knife.

"The defendant then picked the victim up, held her and then slit her throat with the knife," he said.

Officers who attended the gruesome scene have been offered counselling with Oak Lawn police chief Mike Murray saying he has "never seen anything like it."

Ms Giedrocz's attorney said she has lived in the US since 1983 and is a naturalised citizen.